I read the fear in your words. I read the frustrations and the hopelessness. I have been there.
The best advice I can give, is to retrieve yourself away from your son for a long time. I did this with my father, I shut him out completely even though we lived in the same city.
I blocked his number from my phone and never answered unknown phone numbers. I chose this route the last few years of him terrorizing me because he knew how to get to my heart, he knew how pull me in where I felt guilty. He knew how to turn the tables, then saying I love you and when I didn’t help, he would threaten to kill himself if I didn’t cave into his demands. Of course I was a mess, but at the end I told him go ahead and guess what? He didn’t. It was the addiction bluffing.
In these times you have to remember the last time you helped him, it did nothing, but allowed him to gamble again.
He is so deep in the addiction that there is nothing you or anyone can do. He does not have the desire to stop, his desire is to continue to gamble.
I realized through the years, the best defense is our recovery. Be good to you, vowing to never feed into the addiction. Remembering we have to often take extreme measures not to be abused by the addiction.